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  • Invoke Python modules from Java

    - by user36813
    I have a Python interface of a graph library written in C - igraph (the name of library). My need is to invoke the python modules pertaining to this graph library from Java code. It goes like this, the core of library is in c. This core has been imported into Python and interfaces to the functions embedded in core are available in Python. My project's rest of the code is in Java and hence I would like to call the graph functions by Java as well. Jython - which lets you invoke python modules with in Java was an option.I went on trying Jython to discover that it will not work in my case as the core code is in C and Jython wont support anything that is imported as a c dll in python code.I also thought of opting for the approach of calling graph routines directly in c. That is without passing through Python code. I am assuming there must be something which lets you call c code from Java, how ever I am not good in C hence I did not go for it. My last resort seems to execute Python interpreter from command line using Java. But that is a dirty and shameless. Also to deal with the results produced by Python code I will have to write the results in a file and read it back in java. Again dirty way. Is there something that any one can suggest me? Thanks to every one giving time. Thanks Igal for answering. I had a look at it. At first glance it appears as if it is simply calling the python script. Jep jep = new Jep(false, SCRIPT_PATH, cl); jep.set("query", query); jep.runScript(SCRIPT_PATH + file); jep.close(); Isnt it very similar to what we would do if called the python interpreter from command line through a Java code. Runtime runtime = Runtime.getRuntime(); Process proc = runtime.exec("python test.py"); Concern is how do I use the results generated by Python script. The naive way is to write them to file and read it back in Java. I am searching for a smarter approach.Thanks for suggestion anyway.

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  • List of objects or parallel arrays of properties?

    - by Headcrab
    The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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  • Python server does not excecute PHP script: permission denied

    - by krisvandenbergh
    I am trying to execute a PHP file through a Python server. However, I get the following error: File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/CGIHTTPServer.py", line 255, in run_cgi os.execve(scriptfile, args, os.environ) OSError: [Errno 13] Permission denied The python server is running though. What have I done so far? Chmod'ed recursively all directories to (chmod -R a+x) (I know this is not secure but its just for testing purposes) for both Python installation directories and my scripts. Tried to find out if python server is running as root through ps aux grep py I am out of ideas. What could be going wrong else? Thanks for the feedback.

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  • Installing TKInter for Python 2.6.5

    - by Azfar
    Well today's been a bit of shock. After running port -v selfupdate followed by an attempt to run sudo port install py26-ipython MacPorts went around installing a whole host of stuff, including updating my Python from 2.6.4 to 2.6.5. It's nice but unexpected in a creepy way. So I tried to install TKInter using MacPorts with port search tkinter yielding: py-tkinter @2.4.6 (python, graphics) Python bindings to the Tk widget set py25-tkinter @2.5.4 (python, graphics) This is a stub. tkinter is now built with python25 Found 2 ports. So I tried sudo port install py25-tkinter and then it tries to install Python 2.5.5. There must be an easier way to install TkInter without being faffed around... help please?

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  • How to specify or add directory to Python.h search path during setup.py build/install

    - by ca2longoria
    I'm running Linux, and have downloaded a python module I must install without access to any but my particular /home/user directory (I have no root privileges nor the option to pursue them). This of course requires the Python source. This I've downloaded and have laying around in said user directory. While asking the admin to copy the proper files into /usr/include/python2.7 is the easiest way to go about this, I am hoping for a more general and portable solution to this kind of problem. Changing only data in the module source (MANIFEST.in, README.txt, setup.py, etc.), how might I add an arbitrary directory to the search path for Python.h and friends? (Without a solution, "python setup.py build" will continue returning with the "Python.h: No such file or directory" error) Thank you very much. (Additionally, is it acceptable to post this both here and on StackOverflow?)

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  • Desktop file for my Python script

    - by Jason94
    I would like to make a .desktop file for my Python script, but so far the only thing i have is a clickable icon on my desktop! It does nothing when I click it, so im guessing there is something wrong with the execution :) The desktop file: [Desktop Entry] Version=1.0 Type=Python Exec=/home/user/MyDocs/Python/EasySteer/Main.py Name=EasySteer Icon=steering_wheel X-Icon-Path=/usr/share/icons and I also tried: [Desktop Entry] Version=1.0 Type=Application Exec=/usr/bin/xterm "python /home/user/MyDocs/Python/EasySteer/Main.py" Name=EasySteer Icon=steering_wheel X-Icon-Path=/usr/share/icons But nothing works :D if it matters this is for my Nokia N900 mobile phone that runs Maemo linux, but I think the basics are the same.

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  • What are the packages/libraries I should install before compiling Python from source?

    - by Lennart Regebro
    Once in a while I need to install a new Ubuntu (I used it both for desktop and servers) and I always forget a couple of libraries I should have installed before compiling, meaning I have to recompile, and it's getting annoying. So now I want to make a complete list of all library packages to install before compiling Python (and preferably how optional they are). This is the list I compiled with below help and by digging in setup.py. It is complete for Ubuntu 10.04 and 11.04 at least: build-essential (obviously) libz-dev (also pretty common and essential) libreadline-dev (or the Python prompt is crap) libncursesw5-dev libssl-dev libgdbm-dev libsqlite3-dev libbz2-dev More optional: tk-dev libdb-dev Ubuntu has no packages for v1.8.5 of the Berkeley database, nor (for obvious reasons) the Sun audio hardware, so the bsddb185 and sunaudiodev modules will still not be built on Ubuntu, but all other modules are built with the above packages installed. Python 2.5 and Python 2.6 also needs to have LDFLAGS set on Ubuntu 11.04 and later, to handle the new multi-arch layout: export LDFLAGS="-L/usr/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH)" For Python 2.6 and 2.7 you also need to explicitly enable SSL after running the ./configure script and before running make. In Modules/Setup there are lines like this: #SSL=/usr/local/ssl #_ssl _ssl.c \ # -DUSE_SSL -I$(SSL)/include -I$(SSL)/include/openssl \ # -L$(SSL)/lib -lssl -lcrypto Uncomment these lines and change the SSL variable to /usr: SSL=/usr _ssl _ssl.c \ -DUSE_SSL -I$(SSL)/include -I$(SSL)/include/openssl \ -L$(SSL)/lib -lssl -lcrypto Python 2.6 also needs Modules/_ssl.c modified to be used with OpenSSL 1.0, which is used in Ubuntu 11.10. At around line 300 you'll find this: else if (proto_version == PY_SSL_VERSION_SSL3) self->ctx = SSL_CTX_new(SSLv3_method()); /* Set up context */ else if (proto_version == PY_SSL_VERSION_SSL2) self->ctx = SSL_CTX_new(SSLv2_method()); /* Set up context */ else if (proto_version == PY_SSL_VERSION_SSL23) self->ctx = SSL_CTX_new(SSLv23_method()); /* Set up context */ Change that into: else if (proto_version == PY_SSL_VERSION_SSL3) self->ctx = SSL_CTX_new(SSLv3_method()); /* Set up context */ #ifndef OPENSSL_NO_SSL2 else if (proto_version == PY_SSL_VERSION_SSL2) self->ctx = SSL_CTX_new(SSLv2_method()); /* Set up context */ #endif else if (proto_version == PY_SSL_VERSION_SSL23) self->ctx = SSL_CTX_new(SSLv23_method()); /* Set up context */ This disables SSL_v2 support, which apparently is gone in OpenSSL1.0.

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  • [UNIX] Sort lines of massive file by number of words on line (ideally in parallel)

    - by conradlee
    I am working on a community detection algorithm for analyzing social network data from Facebook. The first task, detecting all cliques in the graph, can be done efficiently in parallel, and leaves me with an output like this: 17118 17136 17392 17064 17093 17376 17118 17136 17356 17318 12345 17118 17136 17356 17283 17007 17059 17116 Each of these lines represents a unique clique (a collection of node ids), and I want to sort these lines in descending order by the number of ids per line. In the case of the example above, here's what the output should look like: 17118 17136 17356 17318 12345 17118 17136 17356 17283 17118 17136 17392 17064 17093 17376 17007 17059 17116 (Ties---i.e., lines with the same number of ids---can be sorted arbitrarily.) What is the most efficient way of sorting these lines. Keep the following points in mind: The file I want to sort could be larger than the physical memory of the machine Most of the machines that I'm running this on have several processors, so a parallel solution would be ideal An ideal solution would just be a shell script (probably using sort), but I'm open to simple solutions in python or perl (or any language, as long as it makes the task simple) This task is in some sense very easy---I'm not just looking for any old solution, but rather for a simple and above all efficient solution

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  • Perl Parallel::ForkManager wait_all_children() takes excessively long time

    - by zhang18
    I have a script that uses Parallel::ForkManager. However, the wait_all_children() process takes incredibly long time even after all child-processes are completed. The way I know is by printing out some timestamps (see below). Does anyone have any idea what might be causing this (I have 16 CPU cores on my machine)? my $pm = Parallel::ForkManager->new(16) for my $i (1..16) { $pm->start($i) and next; ... do something within the child-process ... print (scalar localtime), " Process $i completed.\n"; $pm->finish(); } print (scalar localtime), " Waiting for some child process to finish.\n"; $pm->wait_all_children(); print (scalar localtime), " All processes finished.\n"; Clearly, I'll get the Waiting for some child process to finish message first, with a timestamp of, say, 7:08:35. Then I'll get a list of Process i completed messages, with the last one at 7:10:30. However, I do not receive the message All Processes finished until 7:16:33(!). Why is that 6-minute delay between 7:10:30 and 7:16:33? Thx!

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  • Parallel version of loop not faster than serial version

    - by Il-Bhima
    I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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  • Parallel.For Batching

    - by chibacity
    Is there built-in support in the TPL for batching operations? I was recently playing with a routine to carry out character replacement on a character array which required a lookup table i.e. transliteration: for (int i = 0; i < chars.Length; i++) { char replaceChar; if (lookup.TryGetValue(chars[i], out replaceChar)) { chars[i] = replaceChar; } } I could see that this could be trivially parallelized, so jumped in with a first stab which I knew would perform worse as the tasks were too fine-grained: Parallel.For(0, chars.Length, i => { char replaceChar; if (lookup.TryGetValue(chars[i], out replaceChar)) { chars[i] = replaceChar; } }); I then reworked the algorithm to use batching so that the work could be chunked onto different threads in less fine-grained batches. This made use of threads as expected and I got some near linear speed up. I'm sure that there must be built-in support for batching in the TPL. What is the syntax, and how do I use it? const int CharBatch = 100; int charLen = chars.Length; Parallel.For(0, ((charLen / CharBatch) + 1), i => { int batchUpper = ((i + 1) * CharBatch); for (int j = i * CharBatch; j < batchUpper && j < charLen; j++) { char replaceChar; if (lookup.TryGetValue(chars[j], out replaceChar)) { chars[j] = replaceChar; } } });

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  • Build OpenGL model in parallel?

    - by Brendan Long
    I have a program which draws some terrain and simulates water flowing over it (in a cheap and easy way). Updating the water was easy to parallelize using OpenMP, so I can do ~50 updates per second. The problem is that even with a small amounts of water, my draws per second are very very low (starts at 5 and drops to around 2 once there's a significant amount of water). It's not a problem with the video card because the terrain is more complicated and gets drawn so quickly that boost::timer tells me that I get infinity draws per second if I turn the water off. It may be related to memory bandwidth though (since I assume the model stays on the card and doesn't have to be transfered every time). What I'm concerned about is that on every draw, I'm calling glVertex3f() about a million times (max size is 450*600, 4 vertices each), and it's done entirely sequentially because Glut won't let me call anything in parallel. So.. is if there's some way of building the list in parallel and then passing it to OpenGL all at once? Or some other way of making it draw this faster? Am I using the wrong method (besides the obvious "use less vertices")?

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  • How do I unescape HTML entities in a string in Python 3.1?

    - by Sho Minamimoto
    I have looked all around and only found solutions for python 2.6 and earlier, NOTHING on how to do this in python 3.X. (I only have access to Win7 box.) I HAVE to be able to do this in 3.1 and preferably without external libraries. Currently, I have httplib2 installed and access to command-prompt curl (that's how I'm getting the source code for pages). Unfortunately, curl does not decode html entities, as far as I know, I couldn't find a command to decode it in the documentation. YES, I've tried to get Beautiful Soup to work, MANY TIMES without success in 3.X. If you could provide EXPLICIT instructions on how to get it to work in python 3 in MS Windows environment, I would be very grateful. So, to be clear, I need to turn strings like this: Suzy &amp; John into a string like this: "Suzy & John".

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  • When and why are you planning to upgrade to Python 3.0?

    - by Tomislav Mutak
    Python 3.0 (aka Python 3000, Py3k, etc) is now available. When and why are you planning on porting your project or code to the new Python? edit: I'm particularly interested in any features that don't exist in 2.6 that make porting worth it. Right now seems like a lot of negatives (x hasn't been ported yet), but I don't know what people see as the positives. Regarding "when", I'm interested in people's thoughts that the first step to porting is to have "excellent test coverage" which seems a bit optimistic for some projects.

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  • Are there any Python reference counting/garbage collection gotchas when dealing with C code?

    - by Jason Baker
    Just for the sheer heck of it, I've decided to create a Scheme binding to libpython so you can embed Python in Scheme programs. I'm already able to call into Python's C API, but I haven't really thought about memory management. The way mzscheme's FFI works is that I can call a function, and if that function returns a pointer to a PyObject, then I can have it automatically increment the reference count. Then, I can register a finalizer that will decrement the reference count when the Scheme object gets garbage collected. I've looked at the documentation for reference counting, and don't see any problems with this at first glance (although it may be sub-optimal in some cases). Are there any gotchas I'm missing? Also, I'm having trouble making heads or tails of the cyclic garbage collector documentation. What things will I need to bear in mind here? In particular, how do I make Python aware that I have a reference to something so it doesn't collect it while I'm still using it?

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  • How do I set sys.excepthook to invoke pdb globally in python?

    - by saffsd
    From Python docs: sys.excepthook(type, value, traceback)¶ This function prints out a given traceback and exception to sys.stderr. When an exception is raised and uncaught, the interpreter calls sys.excepthook with three arguments, the exception class, exception instance, and a traceback object. In an interactive session this happens just before control is returned to the prompt; in a Python program this happens just before the program exits. The handling of such top-level exceptions can be customized by assigning another three-argument function to sys.excepthook. http://docs.python.org/library/sys.html How do I modify this globally so the default action is to always invoke pdb? Is there a configuration file I can change? I don't want to wrap my code to do this.

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  • 2D animation example in pyglet (python) looping through 2 images/sprites every x seconds

    - by Bentley4
    Suppose you have two images: step1.png and step2.png . Can anyone show me a very simple example in pyglet how to loop through those 2 images say every 0.5 seconds? The character doesn't have to move, just a simple black screen with a fixed region wherein the two images continually change every 0.5 secs. I know how to make a character move, shoot projectiles etc. but I just can't figure out how to control the looping speed of the images.

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  • How to make an arc'd, but not mario-like jump in python, pygame [duplicate]

    - by PythonInProgress
    This question already has an answer here: Arc'd jumping method? 2 answers Analysis of Mario game Physics [closed] 6 answers I have looked at many, many questions similar to this, and cannot find a simple answer that includes the needed code. What i am trying to do is raise the y value of a square for a certain amount of time, then raise it a bit more, then a bit more, then lower it twice. I cant figure out how to use acceleration/friction, and might want to do that too. P.S. - can someone tell me if i should post this on stackoverflow or not? Thanks all! Edit: What i am looking for is not mario-like physics, but a simple equation that can be used to increase then decrease height over the time over a few seconds.

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  • Linear Search in Python? [closed]

    - by POTUS
    def find_interval(mesh,x): '''This function finds the interval containing x according to the following rules, mesh is an ordered list with n numbers return 0 if x < mesh[0] return n if mesh[n-1] < x return k if mesh[k-1] <= x < mesh[k] return n-1 if mesh[n-2] <= x <= mesh[n-1] This function does a Linear search. 08/29/2012 ''' for n in range(len(mesh)): for k in range(len(mesh)): if x == mesh[n]: print "Found x at index:" return n elif x<mesh[n]: return 0 elif mesh[n-1]<x: return n elif mesh[n-2]<=x<=mesh[n-1]: return n-1 elif mesh[k-1]<=x<mesh[k]: return k mesh = [0, 0.1, 0.25, 0.5, 0.6, 0.75, 0.9, 1] print mesh print find_interval(mesh, -1) print find_interval(mesh, 0) print find_interval(mesh, 0.1) print find_interval(mesh, 0.8) print find_interval(mesh, 0.9) print find_interval(mesh, 1) print find_interval(mesh, 1.01) Output: [0, 0.100000000000000, 0.250000000000000, 0.500000000000000, 0.600000000000000, 0.750000000000000, 0.900000000000000, 1] 0 Found x at index: 0 2 6 -1 -1 0 I don't think the output is correct. Can anyone help me fix it? Thanks.

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  • Multiple sites with the same codebase in Python

    - by Jimmy
    I am trying to run a large amount of sites which share about 90% of their code. They are simply designed to query an API and return the results. They will have a common userbase / database but will be configured slightly different and will have different CSS (perhaps even different templating). My initial idea was to run them as separate applications with a common library but I have read about the sites framework which would allow them to run from a single instance of Django which may help to reduce memory usage. https://docs.djangoproject.com/en/dev/ref/contrib/sites/ Is the site framework the right approach to a problem like this, and does it have real benefits over running separate applications? Initially I thought it was, but now I think otherwise. I have heard the following: Your SITE_ID is set in settings.py, so in order to have multiple sites, you need multiple settings.py configurations, which means multiple distinct processes/instances. You can of course share the code base between them, but each site will need a dedicated worker / WSGIDaemon to serve the site. This effectively removes any benefit of running multiple sites under one hood, if each site needs a UWSGI instance running. Alternative ideas of systems: https://github.com/iivvoo/django_layers https://github.com/shestera/django-multisite I don't know what route to be taking with this.

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  • SQLite with two python processes accessing it: one reading, one writing

    - by BBnyc
    I'm developing a small system with two components: one polls data from an internet resource and translates it into sql data to persist it locally; the second one reads that sql data from the local instance and serves it via json and a restful api. I was originally planning to persist the data with postgresql, but because the application will have a very low-volume of data to store and traffic to serve, I thought that was overkill. Is SQLite up to the job? I love the idea of the small footprint and no need to maintain yet another sql server for this one task, but am concerned about concurrency. It seems that with write ahead logging enabled, concurrently reading and writing a SQLite database can happen without locking either process out of the database. Can a single SQLite instance sustain two concurrent processes accessing it, if only one reads and the other writes? I started writing the code but was wondering if this is a misapplication of SQLite.

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  • Python response parse [migrated]

    - by Pavel Shevelyov
    When I'm sending some data on host: r = urllib2.Request(url, data = data, headers = headers) page = urllib2.urlopen(r) print page.read() I have something like this: [{"command":"settings","settings":{"basePath":"\/","ajaxPageState":{"theme":"spsr","theme_token":"kRHUhchUVpxAMYL8Y8IoyYIcX0cPrUstziAi8gSmMYk","css":[]},"ajax":{"edit-submit":{"callback":"spsr_calculator_form_ajax","wrapper":"calculator_form","method":"replaceWith","event":"mousedown","keypress":true,"url":"\/ru\/system\/ajax","submit":{"_triggering_element_name":"submit"}}}},"merge":true},{"command":"insert","method":null,"selector":null,"data":"\u003cdiv id=\"calculator_form\"\u003e\u003cform action=\"\/ru\/service\/calculator\" method=\"post\" id=\"spsr-calculator-form\" accept-charset=\"UTF-8\"\u003e\u003cdiv\u003e\u003cinput id=\"edit-from-ship-region-id\" type=\"hidden\" name=\"from_ship_region_id\" value=\"\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_build_id\" value=\"form-0RK_WFli4b2kUDTxpoqsGPp14B_0yf6Fz9x7UK-T3w8\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_id\" value=\"spsr_calculator_form\" \/\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"bg_p\"\u003e \n\u0421\u0435\u0439\u0447\u0430\u0441 \u0412\u044b... bla bla bla but I want have something, like this: <html><h1>bla bla bla</h1></html> How can I do it?

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  • What does the python Codecs module do?

    - by Aerovistae
    I just read through the documentation on the Codecs module, but I guess my knowledge/experience of comp sci doesn't run deep enough yet for me to comprehend it. It's for dealing with encoding/decoding, especially Unicode, and while to many of you that's a complete and perfect explanation, to me that's really vague. I don't really understand what it means at all. Text is text is text in a .txt file? Or so this amateur thought. Can anyone explain?

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  • Multithreading for a mixed-genre game in Python?

    - by arrogantc
    So here's the situation. I'm making a game that mixes two genres; arcade shooter and puzzler. They don't intertwine TOO much; all the interaction that really goes on is that every time an enemy is destroyed, a block is created. The blocks aren't even a part of the main collision detection system; they have their own more suited to their needs. What I want to ask is this; might it be a good idea to have the arcade shooter portion run on one thread, and the puzzle game portion run on another?

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  • Are python's cryptographic modules good enough?

    - by Aerovistae
    I mean, say you were writing professional grade software that would involve sensitive client information. (Take this in the context of me being an amateur programmer.) Would you use hlib and hmac? Are they good enough to secure data? Or would you write something fancier by hand? Edit: In context of those libraries containing more or less the best hashing algorithms in the world, I guess it's silly to ask if you'd "write something fancier." What I'm really asking here is whether it's enough on its own.

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